Process for producing molded article

ABSTRACT

Process for producing a molded article comprising pouring or injecting a liquid molding material into a mold in the presence of a surface-treating agent comprising a contact angle-reducing substance under the condition that the contact angle between the liquid molding material and the inner surface of the mold is not more than 30°, and curing the liquid molding material; surface-treating agent comprising a contact angle-reducing substance which reduces the contact angle between the liquid molding material and a flat plate made of the same material as the mold to not more than 30°; method for reducing surface voids during molding, comprising using the above surface-treating agent; and use of the above surface-treating agent for reducing surface voids. The molded article has a shape accurately corresponding to the shape of an inner surface of a mold.

This application is the national phase under 35 U.S.C. §371 of PCTInternational Application No. PCT/JP99/02259 which has an Internationalfiling date of Apr. 27, 1999, which designated the United States ofAmerica.

TECHNICAL FIELD

The present invention is directed to a process for producing a moldedarticle, and more particularly to a process for producing a moldedarticle, capable of producing a molded article having a shape accuratelycorresponding to the shape of an inner surface of a mold, and asurface-treating agent used in the process.

BACKGROUND ART

When a molded article is produced by pouring or injecting a liquidmolding material into a mold, and curing the liquid molding material, amold releasing agent has been hitherto applied to the inner surface ofthe mold in order to easily release a molded article from the mold.

However, when a mold releasing agent is applied to the inner surface ofa mold having a complicated shape on its inner surface, and a moldedarticle is produced, the surface properties of the molded article aresometimes deteriorated because so-called surface void, i.e. surfacedefect caused by insufficient filling of the liquid starting materialsand/or foams into the mold having a complicated shape on its innersurface is generated.

An object of the present invention is to provide a process for producinga molded article, capable of producing a molded article having a shapeaccurately corresponding to the shape of an inner surface of a mold,without the generation of defects which lower the surface properties ofa molded article, such as surface void on the surface of the moldedarticle.

The above and other objects of the present invention will be apparentfrom the following description.

DISCLOSURE OF INVENTION

The present invention is directed to the following:

[1] a process for producing a molded article comprising,

(A) pouring or injecting a liquid molding material into a mold in thepresence of a surface-treating agent comprising a contact angle-reducingsubstance under the condition that the contact angle between the liquidmolding material and the inner surface of the mold is not more than 30°,and

(B) curing the liquid molding material;

[2] a surface-treating agent used in a process for producing a moldedarticle comprising pouring or injecting a liquid molding material into amold and curing the liquid molding material, comprising a contactangle-reducing substance which reduces the contact angle between theliquid molding material and a flat plate made of the same material asthe mold to not more than 30°, when the liquid molding materialcontaining the surface-treating agent is dropped on the flat plate, orwhen the surface-treating agent is applied to the flat plate and theliquid molding material is dropped thereon;

[3] a method for reducing surface voids during molding, comprising usingthe above surface-treating agent; and

[4] use of the above surface-treating agent for reducing surface voids.

BEST MODE FOR CARRYING OUT THE INVENTION

Typical examples of the liquid molding materials are resins such aspolyurethanes, epoxy resins, phenolic resins, polyesters, urea resins,olefinic resins such as polyethylenes and polypropylenes, and styrenicresins; rubbers such as natural rubbers, isoprene rubbers, chloroprenerubbers, styrene-butadiene rubbers, butadiene rubbers,acrylonitrile-butadiene rubbers, ethylene-propylene rubbers, butylrubbers, and acrylic rubbers.

The liquid molding materials can be those which are foamed duringmolding to give a foamed molded article. The liquid molding materialswhich give a foamed molded article include self-foamable polyurethanes,foamable olefinic resins, foamable styrene resins, or the like. When theolefinic resins, the styrene resins, or the like are used, there can beemployed a process comprising foaming pre-foamed resin particles, or aprocess comprising impregnating a foaming agent into those resins, andthereafter molding and foaming the resins in a mold.

The process of the present invention exhibits excellent effects forliquid molding materials, particularly polyurethanes, the surfaceproperties of which are easily deteriorated during molding. Typicalexamples of the polyurethanes are, for instance, polyetherpolyurethanes, polyester polyurethanes, and the like.

The starting materials for the polyurethane are not particularlylimited, and known ones can be used. It is desired that the startingmaterials for the polyurethane are a polyol solution and an isocyanateprepolymer. The polyol solution comprises a polyol component, such as apolyether-polyol or a polyester-polyol, a chain extender, water, a foamstabilizer (a surfactant), and, as occasion demands, a catalyst. Theisocyanate prepolymer can be prepared from a polyol component such as apolyether-polyol or a polyester-polyol, and a polyisocyanate componentsuch as methylenediphenyl diisocyanate or a modified compound thereof.The polyether-polyol, the polyester-polyol, the chain extender, the foamstabilizer (a surfactant), the catalyst, the polyisocyanate component,and the isocyanate prepolymer may be those which are known. The contactangle-reducing substance can be contained in the isocyanate prepolymerand/or the polyol solution, and it is desired that the contactangle-reducing substance is contained in the isocyanate prepolymer. Thecontent of the contact angle-reducing substance in the isocyanateprepolymer is preferably 0.1 to 7% by weight, more preferably 0.1 to 5%by weight.

The polyurethane foam containing the contact angle-reducing substancecan be produced by reacting the polyol component with components such asthe polyisocyanate component, the isocyanate prepolymer, and as occasiondemands, water, a chain extender, a foam stabilizer (a surfactant), acatalyst, and the like, in the presence of the contact angle-reducingsubstance.

In the present invention, one of the major features resides in that theliquid molding material is poured or injected into a mold in thepresence of a surface-treating agent comprising a contact angle-reducingsubstance under the condition that the contact angle between the liquidmolding material and the inner surface of the mold is not more than 30°,and the liquid molding material is cured. When molded under thiscondition, there can be exhibited an excellent effect that a moldedarticle having a shape accurately corresponding to the shape of theinner surface of a mold can be produced, without the generation ofsurface voids in the molded article. The reasons why this excellenteffect is exhibited are not clear, but it is presumably based on thefollowing. When the contact angle between the liquid molding materialand the inner surface of the mold is reduced to not more than 30°, thewettability of the mold by the liquid molding material is improved, andthereby the friction between the liquid molding material and the mold isreduced. As a result, the liquid molding material can flow into the moldto follow the complicated shape of the inner surface of the mold. It isdesired that the contact angle between the liquid molding material andthe inner surface of the mold is not more than 23°, particularly notmore than 21°, from the viewpoint of the reducing surface voids of theresulting molded article.

It is desired that the surface-treating agent comprises a contactangle-reducing substance, which reduces the contact angle between theliquid molding material and a flat plate made of the same material asthe mold to not more than 30° when the liquid molding materialcontaining the surface-treating agent is dropped on the flat plate, orwhen the surface-treating agent is applied to the flat plate and theliquid molding material is dropped thereon. When this surface-treatingagent is used, surface voids during molding can be reduced. Moreconcretely, when the surface-treating agent is used, there can beexhibited an excellent effect that a molded article having a shapeaccurately corresponding to the shape of the inner surface of the moldcan be easily produced without the generation of surface voids in theresulting molded article. The reasons why this excellent effect isexhibited are not clear, but it is presumably based on the following.The wettability of the mold by the liquid molding material is improvedby the surface-treating agent, and thereby the friction between theliquid molding material and the mold is reduced. As a result, the liquidmolding material can flow into the mold to follow the complicated shapeof the inner surface of the mold. It is desired that the contact anglebetween the surface-treating agent and the inner surface of the mold isnot more than 23°, particularly not more than 21°.

The contact angle can be determined in accordance with the followingprocedures.

1) The measurement atmosphere is kept windless at 25° C. and 55% RH.

2) As the flat plate made of the same material as the mold, an aluminumplate [average roughness Ra: 0.2-0.4 μm] is horizontally arranged.Thereafter, a silicone mold releasing agent is sprayed on its surface,and sufficiently wiped off with a waste cloth.

3) A given surface-treating agent is uniformly sprayed in the amount of10 g/m² on the silicone mold releasing agent-sprayed surface(surface-treating agents which are solid at 25° C. are previously heatedto a temperature not lower than their melting points to melt and thensprayed).

4) The liquid molding material previously degassed by evacuation iscollected with a syringe, and one droplet is dropped on the flat platefrom the height of 10 cm from the surface of the flat plate in a mannerso that the droplet of the liquid molding material has the weight of0.10±0.02 g.

5) The time at which the droplet reaches the surface of the flat plateis counted as zero second. The change of the droplet is observed inaccordance with the passage of time from the sideways direction of thedroplet with a microscope as a CCD camera. After 60 seconds passed, thecontact angle between the droplet and the flat plate is measured.

Examples of the contact angle-reducing substance include at least onecompound selected from the group consisting of esters, ethers andamides, each having a boiling point of not less than 50° C., preferablynot less than 100° C. at normal pressure, in particular a boiling pointof not less than 100° C. at normal pressure and a boiling point of notmore than 300° C. under the pressure of 0.133 kPa. Among the contactangle-reducing substances, those having vapor pressures of a level whichdoes not completely evaporate within the working hours are preferable.

Examples of the ester having a boiling point of not less than 50° C.include alkyl stearates wherein an alcohol residue moiety of the esterhas 1 to 22 carbon atoms, such as ethyl stearate and butyl stearate;alkyl acetates wherein an alcohol residue moiety of the ester has 4 to22 carbon atoms, such as decyl acetate and octadecyl acetate; alkyloleates wherein an alcohol residue moiety of the ester has 1 to 22carbon atoms, such as methyl oleate and butyl oleate; and other alkylesters of fatty acids wherein the fatty acid residue moiety of the esterhas an alkyl group of 2 to 21 carbon atoms, and the alcohol residuemoiety of the ester has 1 to 22 carbon atoms, such as butyl propionate,butyl 2-ethylhexanoate, ethyl decanoate and methyl linoleate. Thoseesters can be used alone or in an admixture thereof. Among them, fromthe viewpoints of imparting an excellent effect of suppressinggeneration of surface voids to a resulting molded article and thusimproving its appearance (design), alkyl esters of fatty acids, formedfrom a fatty acid and a monohydric alcohol, such as ethyl stearate,butyl stearate, decyl acetate, octadecyl acetate, methyl oleate andbutyl acetate, can be suitably used. Further, it is desired that thefatty acid has 2 to 22 carbon atoms, preferably 2 to 18 carbon atoms,and that the monohydric alcohol has 1 to 22 carbon atoms, preferably 1to 18 carbon atoms. Moreover, it is desired that the total number ofcarbon atoms of the fatty acid and the monohydric alcohol is 10 to 40,preferably 12 to 36. In addition, from the viewpoint of yellowingresistance of the resulting molded article, alkyl esters of saturatedfatty acids, such as butyl stearate and octadecyl acetate, can beparticularly suitably used.

The ester having a boiling point of not less than 50° C. may be asymmetric ether or asymmetric ether. Examples thereof include dioctylether, dibutyl ether, dihexyl ether, didecyl ether, butyl hexyl ether,and the like. Those esters may be used alone or in an admixture thereof.Among them, from the viewpoints of imparting an excellent effect ofsuppressing generation of surface voids to a resulting molded articleand thus improving its appearance (design), dioctyl ether, and the likecan be suitably used.

The content of the contact angle-reducing substance in thesurface-treating agent may be appropriately adjusted so that the contactangle between the liquid molding material and the flat plate is reducedto not more than 30°, preferably not more than 23°, more preferably notmore than 21°. Incidentally, the contact angle-reducing substance itselfcan be solely used as the surface-treating agent, since the contactangle between the liquid molding material and the flat plate can bereduced to not more than 30°, even when the contact angle-reducingsubstance is used alone as the surface-treating agent.

The surface-treating agent may contain a mold releasing agent such as asilicone compound or a wax as occasion demands, in addition to thecontact angle-reducing substance. The surface-treating agent containingthe contact angle-reducing substance and the mold releasing agent can bedesirably used by applying it to the inner surface of the mold duringthe production of various molded articles because this surface-treatingagent suppresses the generation of surface voids, and improves theappearance (design) of the molded article.

The silicone compound can be suitably used in the present inventionbecause the silicone compound is excellent in liquidity and releasingproperties, and moreover is durable for repetitious use. Typicalexamples of the silicone compound include dimethyl silicone oil, andmodified silicone oils such as alkyl-modified silicone oils and higherfatty acid-modified silicone oils, or those diluted with a solvent,those prepared into aqueous emulsions, and the like. Concretely, therecan be cited dimethyl silicone oil having a viscosity of 30 to 5000mm²/s at 25° C. Those silicone compounds can be used alone or in anadmixture thereof.

The wax can be suitably used because it is inexpensive. Examples of thewax include mineral oils, olefinic waxes, paraffin waxes, and the like.Those waxes can be used alone or in admixture thereof. Among them, themineral oils and paraffin waxes each having a molecular weight of notless than 300 are preferable.

Among the mold releasing agents, the silicone compounds are morepreferable from the viewpoint of the releasing property.

The content of the mold releasing agent in the surface-treating agentcannot be absolutely determined because it differs depending upon theirkinds. However, it is desired that the content is usually not less than5% by weight, preferably not less than 10% by weight, more preferablynot less than 30% by weight, from the viewpoint of exhibiting sufficientreleasing properties. Also, it is desired that the content is not morethan 95% by weight, preferably not more than 90% by weight, from theviewpoint of exhibiting sufficient surface properties.

The surface-treating agent can be applied to the inner surface of themold, or it can be contained in the liquid molding material.

When the surface-treating agent is applied to the inner surface of themold, an outsole of shoe soles made of a polyurethane foam havingcomplicated shapes particularly in the bottom surface can be formed in ashape exactly conforming to the mold without the generation of defectswhich impair the surface properties of the molded article, such assurface void.

The method for applying the surface-treating agent to the inner surfaceof the mold includes, for instance, a method of coating, spraying,dipping, or the like, without limiting the present invention to thosemethods above.

When the surface-treating agent is applied to the inner surface of themold, the mold is filled with the liquid molding material thereafter,and can be molded under given molding conditions suitable for the kindsof the liquid molding material, and the like. It is desired that theamount of the surface-treating agent applied to the inner surface of themold is 3 to 30 g/m² from the viewpoints of imparting sufficient surfaceproperties to a resulting molding article and preventing cracking anddulling of the surface.

When the surface-treating agent is contained in the liquid moldingmaterial, a midsole of shoe soles, made of a polyurethane foam andparticularly having a complicated shape in the side surfaces can bemolded in a shape exactly conforming to the mold without the generationof the defects which impair the surface properties of the moldedarticle, such as surface void.

When the surface-treating agent is contained in the liquid moldingmaterial, the content of the surface-treating agent in the liquidmolding material differs depending upon the kinds of the liquid moldingmaterial. However, it is desired that the content is adjusted so thatthe contact angle between the liquid molding material and the flat platemade of the same material as the mold is not more than 30°. Forinstance, it is desired that the content of the contact angle-reducingsubstance in the liquid molding material is 0.05 to 3.5% by weight,preferably 0.25 to 1% by weight.

When the surface-treating agent is contained in the liquid moldingmaterial, the liquid molding material is filled in the mold, and can bemolded under given molding conditions suitable for the kinds of theliquid molding material.

The materials of the mold which can be used in the present invention arenot particularly limited. Examples of such materials include iron,stainless steel, copper, aluminum, aluminum alloys, epoxy resins,phenolic resins, and the like. In addition, the shapes of the innersurface of the mold are not particularly limited, and any arbitraryshape can be selected as long as the inner surface has a shape wellcorresponding to the shape of the desired molded article.

When the liquid molding material is molded in a mold, it is desirable topreviously apply a mold releasing agent to the inner surface of the moldby means of coating, spraying, dipping, or the like in order to improveits releasing property. The mold releasing agent includes dimethylsilicone oil, mineral oils, paraffin waxes, and the like, withoutintending to limit the present invention to those exemplified above.

Thus, a molded article having a given shape can be obtained by moldingand subsequent demolding. The resulting molded article has excellentsurface properties because the generation of harmful defects such assurface void is suppressed even when the molded article has acomplicated shape in its inner surface.

Especially, when the molded article is a molded article made of apolyurethane foam, the above-mentioned effects are exhibited even moreexcellently. Particularly, the above effects are even more remarkablyexhibited for the polyurethane foam for shoe soles having complicatedshapes in the bottom surface or side surfaces.

In general, the shoe soles can be classified into outsoles used insandals and men's shoes, and midsoles used in sports shoes. The effectsaccording to the present invention can be remarkably exhibitedparticularly in midsoles used within a low density region.

From the viewpoint of reducing surface voids, the density of thepolyurethane foam is preferably not less than 0.15 g/cm³ and less than0.30 g/cm³, and more preferably not less than 0.20 g/cm³ and less than0.30 g/cm².

Preparation Example 1 Preparation of Liquid Molding Material forPolyether Polyurethane Foam

In a mixer (Model “DH-2.5,” manufactured by Tokushu Kika Kogyo K.K.)were previously stirred 50 parts by weight of a polyol solution [tradename: “EDDYFOAM AS-2045,” manufactured by Kao Corporation], comprisingpolypropylene glycol, a chain extender, water and a foam stabilizer (asurfactant), and 50 parts by weight of an isocyanate prepolymer [tradename: “EDDYFOAM B-6009N,” manufactured by Kao Corporation], mainconstituents of which were polypropylene glycol and 4,4-diphenylmethanediisocyanate, and the resulting mixture was evacuated in a desiccator.

The resulting liquid mixture was used to measure a contact angle inaccordance with the following method for measurement of a contact angle.As a result, the contact angle was found to be 43°.

The viscosity of this liquid mixture gradually increases. Therefore, thetime period from the previous stirring of the polyol solution and theisocyanate prepolymer to the measurement of the contact angle wasadjusted to four minutes.

Preparation Example 2 Preparation of Liquid Molding Material forPolyester Polyurethane Foam

In a mixer (Model “DH-2.5,” manufactured by Tokushu Kika Kogyo K.K.)were previously stirred 50 parts by weight of a polyol solution [tradename: “EDDYFOAM AS-1210U,” manufactured by Kao Corporation], comprisinga polyester-polyol, a chain extender, water and a foam stabilizer (asurfactant), and 50 parts by weight of an isocyanate prepolymer [tradename: “EDDYFOAM B-2009,” manufactured by Kao Corporation], mainconstituents of which were a polyester-polyol and 4,4-diphenylmethanediisocyanate, and the resulting mixture was evacuated in a desiccator.

The resulting liquid mixture was used to measure a contact angle inaccordance with the following method for measurement of a contact angle.As a result, the contact angle was found to be 46°.

The viscosity of this liquid mixture gradually increases. Therefore, thetime period from the previous stirring of the polyol solution and theisocyanate prepolymer to the measurement of the contact angle wasadjusted to four minutes.

[Measurement of Contact Angle]

1) The measurement atmosphere is kept windless at 25° C. and 55% RH.

2) As the flat plate made of the same material as the mold, an aluminumplate [average roughness Ra: 0.2-0.4 μm] is horizontally arranged.Thereafter, a silicone mold releasing agent [trade name: “PURAPOWER2060,” manufactured by Kao Corporation] is sprayed on its surface, andsufficiently wiped off with a waste cloth.

3) A given surface-treating agent is uniformly sprayed in the amount of10 g/m² on the silicone mold releasing agent-sprayed surface(surface-treating agents which are solid at 25° C. are previously heatedto a temperature of not lower than their melting points to melt and thensprayed).

4) The liquid molding material previously degassed by evacuation iscollected with a syringe [Model “SS-02S,” manufactured by TERUMOCORPORATION], and one droplet is dropped on the flat plate from theheight of 10 cm from the surface of the flat plate in a manner so thatthe droplet of the liquid molding material has the weight of 0.10±0.02g.

5) The time at which the droplet reaches the surface of the flat plateis counted as zero second. The change of the droplet is observed inaccordance with the passage of time from the sideways direction of thedroplet with a microscope [Product No. “VH-6200,” manufactured byKEYENCE CORPORATION] as a CCD camera. After 60 seconds passed, thecontact angle between the droplet and the flat plate is measured.

EXAMPLES 1 TO 4 Comparative Examples 1 to 4

[Production of Molded Articles Made of Polyether Polyurethane Foam]

There was used a mold for testing made of aluminum having an innersurface for forming on the tiptoe portion a sole pattern having 127projections for antislipping wherein each of their height, width andlength is about 5 mm, respectively, and wherein each vertical crosssection of the projections was triangular. The temperature of the moldwas adjusted to 50°±2° C. A mold releasing agent (trade name: “PURAPOWER2060,” manufactured by Kao Corporation) was sprayed on the innersurface, and wiped off with a waste cloth.

A surface-treating agent shown in Table 1 was used, and sprayed on themold releasing agent-sprayed surface with a spray gun so that the amountof the surface treatment agent applied was 10 g/m². The contact anglebetween the liquid molding material and the surface-treatingagent-sprayed surface was measured in accordance with the above methodfor measurement of a contact angle. The results are shown in Table 1.

One tank of a pouring-type low-pressure foaming machine was charged withan isocyanate prepolymer [trade name: “EDDYFOAM B-6009N,” manufacturedby Kao Corporation], and the liquid temperature was adjusted to 40° C.,and the other tank thereof was charged with a liquid mixture prepared bymixing 100 parts by weight of a polyol composition solution [trade name:“EDDYFOAM AS-2045,” manufactured by Kao Corporation] and 2 parts byweight of a catalyst [trade name: “EDDYFOAM AS-651-60C,” manufactured byKao Corporation], and the liquid temperature was adjusted to 40° C.

The isocyanate prepolymer was admixed with the liquid mixture, and theresulting mixture was stirred using this low-pressure foaming machine,so that an isocyanate index was 98. The resulting mixture was pouredinto the mold mentioned above to allow foaming. After 5 minutes passedfrom the pouring, the foamed product was taken out from the mold, togive a molded article made of a polyurethane foam. Each of the resultingmolded articles had a density of about 0.65 g/cm³ and hardness (Asker C)of 80±2.

Next, the shape transfer ratio of the resulting molded article made of apolyurethane foam was evaluated in accordance with the following method.The results are shown in Table 1.

[Shape Transfer Ratio]

In order to determine whether or not a molded article having a shapeaccurately corresponding to the shape of the inner surface of the moldis obtained, the shape transfer ratio was obtained in accordance withthe following method.

The case where not less than 50% of the projections for antislipping ofthe molded article was lacked at its tip portion was evaluated as Score−3, and the number of the lacked projections is defined as “p”; the casewhere not less than 30% and less than 50% of the projections forantislipping of the molded article was lacked at its tip portion wasevaluated as Score −2, and the number of the lacked projections isdefined as “q”; the case where less than 30% of the projections forantislipping of the molded article was lacked at its tip portion wasevaluated as Score −1, and the number of the lacked projections isdefined as “r”; and the case where no lacked portions were observed wasevaluated as Score 0, and the number of no lacked projections is definedas “s” (the total number of p+q+r+s is 127. The shape transfer ratio wascalculated in accordance with the following equation:

[Shape Transfer Ratio]=[381+(−3)×p+(−2)×q+(−1)×r+0×s]÷3.81

EXAMPLES 5 TO 8 Comparative Examples 5 to 8

[Production of Molded Articles Made of Polyester Polyurethane Foam]

The same procedures as in Examples 1 to 4 were carried out except thatan isocyanate prepolymer [trade name: “EDDYFOAM B-2009,” manufactured byKao Corporation], and 100 parts by weight of a polyol solution [tradename: “EDDYFOAM AS-1210,” manufactured by Kao Corporation] and 1.5 partsby weight of a catalyst [trade name: “EDDYFOAM AS-651-60C,” manufacturedby Kao Corporation], instead of the isocyanate prepolymer, the polyolsolution and the catalyst used in Examples 1 to 4, to produce a moldedarticle made of a polyurethane foam. Each of the resulting moldedarticles had a density of about 0.60 g/cm³ and hardness (Asker C) of80±2.

The shape transfer ratio of the resulting molded article made of apolyurethane foam was evaluated in the same manner as above. The resultsare shown in Table 1.

TABLE 1 Contact Angle Shape Kind of Composition of after TransferExample Polyurethane Surface-Treating Agent 60 sec. Ratio No. Foam (% byweight) (° C.) (%) Example 1 Ether Butyl stearate (100) 18 93.5Polyurethane 2 Ether Ethyl stearate (100) 17 94.6 Polyurethane 3 EtherOctadecyl stearate (100) 17 95.5 Polyurethane 4 Ether Dioctyl ether(100) 17 97.7 Polyurethane Comp. Ex. 1 Ether None 43 34.9 Polyurethane 2Ether EMULGEN 903*¹ (100) 32 50.3 Polyurethane 3 Ether Linseed oil (100)31 57.5 Polyurethane 4 Ether Lard (100) 34 44.6 Polyurethane Example 5Ester Butyl stearate (100) 21 86.3 Polyurethane 6 Ester Ethyl stearate(100) 23 83.6 Polyurethane 7 Ester Octadecyl stearate (100) 22 83.6Polyurethane 8 Ester Dioctyl ether (100) 22 90.2 Polyurethane Comp. Ex.5 Ester None 46 30.3 Polyurethane 6 Ester EMULGEN 903*¹ (100) 34 46.3Polyurethane 7 Ester Linseed oil (100) 34 53.3 Polyurethane 8 Ester Lard(100) 35 42.1 Polyurethane (Note) *¹Trade name, manufactured by KaoCorporation

As is clear from the results shown in Table 1, it can be seen that allof the molded articles obtained in each Example have extremely highshape transfer ratios of because a contact angle-reducing substanceshowing a contact angle of not more than 30° is used.

EXAMPLES 9 TO 20 Comparative Examples 9 to 12

[Production of Molded Articles Made of Polyether Polyurethane Foam]

The same procedures as in Examples 1 to 4 were carried out except thatspraying of the mold releasing agent on the mold for testing was omittedand that surface-treating agents shown in Table 2, which were previouslyadmixed together at 25° C., were used, to produce a molded article madeof a polyurethane foam. Each of the resulting molded articles had adensity of about 0.65 g/cm³ and hardness (Asker C) of 80±2.

The releasing property after production of the molded article made of apolyurethane foam was evaluated in accordance with the following method.The shape transfer ratio of the resulting molded article made of apolyurethane foam was evaluated in the same manner as above. The resultsare shown in Table 2.

[Releasing Property after Production]

The condition when taking out the resulting molded article from the moldwas determined based on the following criteria:

⊚: the molded article not being entirely stuck to the inner surface ofthe mold at all;

∘: the molded article being slightly stuck to the inner surface of themold without posing any problems; and

×: the molded article being stuck to the mold, thereby making itimpossible to take out the molded article from the mold.

EXAMPLES 21 AND 22

[Production of Molded Articles Made of Polyester Polyurethane Foam]

The same procedures as in Examples 5 to 8 were carried out except thatspraying of the mold releasing agent on the mold for testing was omittedand that the surface-treating agents shown in Table 2, which werepreviously admixed together at 25° C. were used, to produce a moldedarticle made of a polyurethane foam. Each of the resulting moldedarticles had a density of about 0.65 g/cm³ and hardness (Asker C) of80±2.

The releasing property after production and the shape transfer ratio ofthe resulting molded article made of a polyurethane foam were evaluatedin the same manner as above. The results are shown in Table 2.

In Table 2, the following mold releasing agents were used: Moldreleasing agent A: [trade name: “SUPER OIL B.” manufactured by NOFCorporation]; Mold releasing agent B: dimethyl silicone oil [trade name:“TSF-451-50,” manufactured by Toshiba Silicone Co., Ltd.]; Moldreleasing agent C: dimethyl silicone oil [trade name: “TSF-451-300,”manufactured by Toshiba Silicone Co., Ltd.]; Mold releasing agent D: ablend of silicone compounds [trade name: “PURAPOWER 20conc 60,”manufactured by Kao Corporation].

TABLE 2 Shape Kind of Composition of Transfer Example PolyurethaneSurface-Treating Agent Releasing Ratio No. Foam (% by weight) Property(%) Example  9 Ether Butyl stearate (10) ⊚ 70.3 Polyurethane Moldreleasing agent A (90) 10 Ether Butyl stearate (20) ⊚ 95.0 PolyurethaneMold releasing agent A (80) 11 Ether Butyl stearate (50) ⊚ 96.3Polyurethane Mold releasing agent A (50) 12 Ether Butyl stearate (80) ◯92.5 Polyurethane Mold releasing agent A (20) 13 Ether Butyl stearate(20) ◯ 92.3 Polyurethane Mold releasing agent A (80) 14 Ether Butylstearate (20) ⊚ 96.3 Polyurethane Mold releasing agent B (80) 15 EtherButyl stearate (20) ⊚ 92.8 Polyurethane Mold releasing agent C (80) 16Ether Butyl stearate (20) ⊚ 89.3 Polyurethane Mold releasing agent D(80) 17 Ether Dioctyl ether (20) ◯ 93.6 Polyurethane Mold releasingagent A (80) 18 Ether Dioctyl ether (20) ⊚ 98.5 Polyurethane Moldreleasing agent B (80) 19 Ether Dioctyl ether (20) ⊚ 95.3 PolyurethaneMold releasing agent C (80) 20 Ether Dioctyl ether (20) ⊚ 91.6Polyurethane Mold releasing agent D (80) Comp. Ex.  9 Ether Moldreleasing agent ⊚ 33.6 Polyurethane A (100) 10 Ether Mold releasingagent ⊚ 35.6 Polyurethane B (100) 11 Ether Mold releasing agent ⊚ 38.3Polyurethane C (100) 12 Ether Mold releasing agent ⊚ 34.2 Polyurethane D(100) Example 21 Ester Butyl stearate (20) ⊚ 83.3 Polyurethane Moldreleasing agent A (80) 22 Ester Dioctyl ether (20) ⊚ 84.6 PolyurethaneMold releasing agent A (80)

As is clear from the results shown in Table 2, it can be seen that eachof the molded articles made of a polyurethane foam obtained in eachExample has an extremely high shape transfer ratio, and also hasexcellent releasing properties after molding because the contactangle-reducing substance showing a contact angle of not more than 30° isused.

EXAMPLES 23 TO 26 Comparative Examples 13 to 15

There was used a mold made of aluminum having a shape corresponding to amolded article having a length of 255 mm, a width of 90 mm, a height of30 mm, and a thickness of 5 mm, and also having 20 projections whereineach of length, width, and height is 20 mm, 20 mm, and 2 mm,respectively, as a design of its side surface. The temperature of themold was adjusted to 70°±2° C. A mold releasing agent (trade name:“PURAPOWER 2060,” manufactured by Kao Corporation) was sprayed on theinner surface, and wiped off with a waste cloth.

A contact angle-reducing substance shown in Table 3 was added to anisocyanate prepolymer [trade name: “EDDYFOAM B-3021,” manufactured byKao Corporation]. One tank of a pouring-type low-pressure foamingmachine was charged with the resulting mixture, and the liquidtemperature was adjusted to 35° C. The other tank thereof was chargedwith a liquid mixture prepared by mixing 100 parts by weight of a polyolsolution [trade name: “EDDYFOAM AS-6-52U,” manufactured by KaoCorporation], 1.3 parts by weight of a catalyst [trade name: “EDDYFOAMAS-651-60C,” manufactured by Kao Corporation], 2 parts by weight of acrosslinking agent [trade name: “EDDYFOAM AS-60E,” manufactured by KaoCorporation], 0.5 parts by weight of a foam stabilizer (a surfactant)[trade name: “EDDYFOAM AS-11S,” manufactured by Kao Corporation], andthe liquid temperature was adjusted to 40° C.

The isocyanate prepolymer was admixed with the liquid mixture andstirred using this low-pressure foaming machine so that an isocyanateindex was 100. The resulting mixture was poured into the mold mentionedabove to allow foaming. After 5 minutes passed from the pouring, thefoamed product was taken out from the mold, to give a molded articlemade of a polyurethane foam. Each of the resulting molded articles had adensity of about 0.28 g/cm³ and hardness (Asker C) of 60±2.

Next, the shape transfer ratio of the resulting molded article made of apolyurethane foam was evaluated in accordance with the following method.The results are shown in Table 3.

When the upper portion of the projections is lacked in the length of notless than 2 mm during the molding of the molded article, its length ismeasured, and a sum (T) of length of all surface voids is calculated,and the shape transfer ratio is calculated from the following equation:

Shape Transfer Ratio=(400=T)÷400×100

The evaluation is made on the following criteria:

Criteria

∘: transfer ratio being not less than 95 (extremely excellentappearance);

Δ: transfer ratio being not less than 92.5 and less than 95 (goodappearance); and

×: transfer ratio being less than 92.5 (poor appearance).

TABLE 3 Contact Angle-Reducing Susbtance Evaluation of and AmountThereof Shape Transfer Example [Content in Isocyanate Prepolymer RatioNo. (% by weight)] (%) Example 23 Butyl stearate (0.5) ∘ 24 Butylstearate (1) ∘ 25 Butyl stearate (5) ∘ 26 Ethyl stearate (1) ∘ Comp. Ex.13 Octyl phthalate (1) x 14 Octyl phthalate (5) x 15 None x

As is clear from the above results shown in Table 3, it can be seen thatall of the molded articles made of a polyurethane foam obtained inExamples 23 to 26 have high shape transfer ratios because the contactangle-reducing substance is added thereto.

INDUSTRIAL APPLICABILITY

According to the process of the present invention, there can beexhibited an effect that a molded article having a shape accuratelycorresponding to the shape of the inner surface of the mold can beproduced without the generation of lowering surface properties such assurface void on the surface of the molded article.

Therefore, the process of the present invention can be suitably employedwhen producing a molded article used, for instance, for shoe soles.

What is claimed is:
 1. A process for producing a molded article made ofa polyurethane comprising: (A) adding a surface-treating agentcomprising a contact angle-reducing substance to an isocyanateprepolymer; (B) mixing a polyol component with said isocyanateprepolymer; (C) pouring or injecting the resulting mixture into a mold;and (D) curing the mixture, to give said molded article; wherein thesurface-treating agent is added to the isocyanate prepolymer under thecondition that the contact angle between the mixture obtained in saidstep (B) and the inner surface of the mold is not more than 30°.
 2. Theprocess of claim 1, wherein said molded article is a shoe sole made of apolyurethane foam.
 3. The process of claim 1, wherein the contactangle-reducing substance is an ester prepared from a fatty acid and amonohydric alcohol.
 4. The process of claim 1, wherein the contact anglebetween the liquid molding material and the inner surface of the mold isadjusted to not more than 23°.
 5. The process of claim 1, wherein a moldreleasing agent is applied to said inner surface of the mold prior topouring or injecting the liquid molding material in the mold.
 6. Theprocess of claim 1, wherein the contact angle-reducing substanceis,contained in the isocyanate prepolymer in an amount of 0.1 to 7% byweight.
 7. A surface-treating agent used in a process for producing amolded article made of a polyurethane comprising: (A) adding asurface-treating agent comprising a contact angle-reducing substance toan isocyanate prepolymer; (B) mixing a polyol component with saidisocyanate prepolymer; (C) pouring or injecting the resulting mixtureinto a mold; and (D) curing the mixture, to give said molded article;wherein the contact angle-reducing substance reduces the contact angleto not more than 30° between the mixture obtained in said step (B) and aflat plate made of the same material as the mold when the mixture isdropped on the flat plate.
 8. The surface-treating agent of claim 7,wherein the molded article is a shoe sole made of a polyurethane foam.